Method of treating mixed sulfid ores.



UNi'rhn STATES PATENT OFFICE.

ERMINIO FERRARIS, OF MONTEPONI, ITALY.

METHOD OF TREATING MIXED SULFID ORES.

SPECIFICATION forming part of Letters Patent N 0. 707,506, dated August 19, 1902.

Application filed July 28, 1902. erial No. 117,390. (No specimens.)

To all whont it may concern.-

Be it known that I, ERMINIO FERRARIS, a subject of the King of Italy, residing at Monteponi, Sardinia, Italy, have invented a certain new and useful Method of Treating Mixed Sulfid Ores, especially those containing zinc, of which the following is a specification.

It is known that mixed sulfid ores may be decomposed with concentrated sulfuric acid, so that the soluble sulfates arising from the reaction may be separated from the insoluble by leaching with water, if the decomposition be effected with the aid of heat and if there be present four molecules of sulfuric acid to each molecule of metallic sulfid.

The present invention consists in the use of only two molecules of sulfuric acid to each molecule of metallic sulfid and the execution of the reaction without the aid of extraneous heat, wherefore the process is rendered significantly cheaper. Moreover, a portion of the sulfur remains uncombined in the sulfurated ore, from which it may be recovered by distillation or by combustion to sulfurous anhydrid in the presence of air. In the former case a valuable by-product (flowers of sulfur) is obtained, while in the latter it is possible to recover as much sulfuric acid as was consumed in the formation of the metallic sulfates.

The best results are obtained when acid of 66 Baum in strength is employed for the decomposition of the ore. This acts energetically upon the finely-pulverized ore, with evolution of heat, according to the equation Each molecule of metallic sulfid in the ore requires two molecules of sulfuric acid, whereby the sulfur of the ore is set free and a molecule of sulfurous anhydrid is developed. When weaker sulfuric acid is employed, the reaction is incomplete and hydrogen sulfid is formed, together with sulfurous anhydrid, which is disadvantageous to the recovery of sulfuric acid. With the use of sulfuric anhydrid no reaction takes place. The decomposition of the ore by concentrated sulfuric acid takes place without the application of extraneous heat and can be performed in any suitable vessel wherein it can be aided by stirring.

If it be desired to drive off the free sulfur and any arsenic that may be present from the sulfated ore, the latter is either heated in a closed muffle or roasted gently in a reverberatory furnace in order to volatilize the sulfur or burn it to sulfurous anhydrid. In the latter case the sulfurous anhydrid is advantageously united with that which is evolved in the first treatment of the ore and employed as the source of sulfuric acid for the decomposition of a fresh lot of ore. In roasting the sulfate of iron is either wholly or partially decomposed, and copper salts, if present, are also partially decomposed and rendered insoluble.

From the sulfated ore all of the zinc can be leached by means of Water, while lead, silver, gold, and antimony will remain in the insoluble residue. Iron and copper go like wise into solution unless the sulfates be roasted and the iron salts be peroxidized by the air; otherwise a part or all of the iron remains in the insoluble residue, according to the extent to which the sulfated ore may be oxidized by exposure to the air before leachmg.

What I claim, and desire to secure by Letters Patent, is-

1. The process of decomposing mixed sulfid ores by means of concentrated sulfuric acid without the aid of extraneous heat.

2. The process of decomposing mixed sulfid ores containing zinc, and the production therefrom of zinc sulfate soluble in water, by means of concentrated sulfuric acid without the aid of extraneous heat.

8. The process of decomposing mixed sulfid ores containing zinc, and the production therefrom of zinc sulfate soluble in water, by means of concentrated sulfuric acid,employed in the ratio of two molecules of the acid to each molecule of the metallic sulfids contained in the ore, without the aid of extraneous heat.

In testimony whereof I affix my signature in presence of two witnesses.

ERMINIO rERRARIs.

lVitnesses:

G. LAVAGUINO, CLEMENTE GIUTIIETTI. 

